ABSTRACT
This chapter targets the reliability of electronics components under high random vibration conditions. Examples include electronics in vehicles, construction equipment, and aircraft. A fatigue life estimation procedure is presented, and each step of procedure is explained. A finite element model of the test vehicle is built in ANSYS. The model is first validated by correlating the natural frequencies, mode shapes, and transmissibility functions from simulation with experimentally measured ones. The model is then used to simulate a random vibration response spectrum at critical solder interconnects. The obtained results are then transformed into time domain, and the number of cycles is counted to determine the effective number of cycles that can then be used to predict fatigue life with Miner’s damage rule. In this chapter we take a look at some of the major issues with electronics packaging under high-vibration environments, namely the application of ball grid arrays (BGAs) on rack-style printed wiring boards (PWBs). There are many factors that affect the BGA components on the circuit board, including
• Placement on the PWB • Vibration level • Temperature level • Solder type
In addition to all these variables, every design is slightly different, with different resonances and requirements. Rack card assemblies do not have the ability to control the PWB resonances around the BGAs like other PWB designs without significant design improvements; the goal is to keep the design simple. Take
ACTEL 484 BGA as an example; BGAs are used for programmable logic devices as well as processors for high amounts of input and output. It is critical to make sure that these programmable logic devices and processors operate under all conditions. Finally, BGAs are unreliable in higher-vibration environments, so a proper understanding of how each of the above variables affects the component is critical to having a good design the first time, and to not run development testing under common environments that are shown in this chapter.
